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What do your hematocrit test results mean?

Cropped SingleCare logo By | May 1, 2020
Medically reviewed by Michael L. Davis, MD

If you’re showing signs of being anemic (which could include fatigue, grumpiness, headaches, or heavy menstrual cycles), your doctor might want to do bloodwork. A hematocrit test is a type of blood test that can detect anemia and other health conditions, which will help your healthcare provider to properly diagnose and treat you. This article describes what hematocrit tests are and helps explain what your hematocrit levels mean.

What is hematocrit?

Hematocrit is a measurement of the size and number of red blood cells that someone has. Everyone’s blood is made up of red blood cells, white blood cells, and platelets. The hematocrit (hct) is a measurement of how much of someone’s blood is made up of red blood cells. The test measures by volume but is then expressed as a percentage. If a person has a hematocrit of 40%, this means that he or she has 40 milliliters of red blood cells in 100 milliliters of blood.

Doctors will ask someone to get a hematocrit test as part of a complete blood count (CBC) to see how well they’re responding to a certain treatment and/or to see if they have any underlying health problems. Hematocrit helps measure hemoglobin, which is what’s found in oxygen-carrying red blood cells. It’s important because the body can’t get enough oxygen to function properly without it, says Susan Besser, MD, a family practitioner at Mercy Medical Center in Baltimore, Maryland.

Why is hematocrit important?

Hematocrit tests can tell doctors if someone is anemic, which is one of the most common reasons for ordering the test. Symptoms of anemia include tiredness, grumpiness, heavy menstrual periods, cold hands and feet, and poor concentration. Your doctor may ask you to get a hematocrit test done if you have any of those symptoms.

Hematocrit tests, which are sometimes called packed cell volume tests (PCV), can also help tell doctors whether someone has other nutritional deficiencies or health problems such as leukemia, kidney disease, or arthritis. Hematocrit tests are important because they measure how many red blood cells someone has. Too many or too few red blood cells can indicate certain nutritional deficiencies or diseases that doctors will know how to identify.

What to expect during a hematocrit test

During a hematocrit test, you can expect to have a sample of blood taken by a phlebotomist or another healthcare professional who can draw blood. Getting your blood drawn can be uncomfortable, but most people only feel a light prick when the needle inserts the vein. If you need to have a hematocrit test done and know that you might get lightheaded, you can always ask to lie down while your blood sample is being taken.

What is a normal hematocrit level?

The average healthy adult should have a normal hematocrit level that ranges between 35% to 50%. A normal hematocrit level for women is 36.1% to 44.3%. For men, a normal range is 40.7% to 50.3%. The normal numbers vary a little from lab to lab. This means the average adult female’s total blood volume should consist of 36% to 44% red blood cells, and the average adult male’s blood should be 40% to 50% red cells. Infants and newborn babies should have normal values that range between 32% to 61%.

Hematocrit tests are generally pretty accurate. Test results help doctors diagnose their patients with the right health condition so they can give appropriate treatment. It’s possible for certain things to cause a hematocrit test to give inaccurate results though. Here are some factors that commonly cause abnormally high or low hematocrit levels:

  • Pregnancy can cause hematocrit levels that are lower than usual
  • Any recent blood transfusions
  • Living at a high altitude can cause high hematocrit levels
  • Dehydration can cause high hematocrit levels

Doctors are aware of what can potentially skew test results, and they have them in the back of their mind when they’re reading results. If your doctor feels that your hematocrit levels may have been affected by something like dehydration, they may ask you to take the test again at a different time.

What does it mean if your hematocrit is low?

Having low hematocrit levels, which is sometimes called anemia, often makes people feel under the weather. If you’re having any of the following symptoms, they could mean you have a low red blood cell count:

  • Tiredness
  • Lack of concentration
  • Shortness of breath
  • Headaches
  • Heavy menstrual cycles
  • Grumpiness

If you take a hematocrit test and your test results report low hematocrit levels, this means you have a lower percentage of red blood cells than you should. Many things can cause low hematocrit levels, which can indicate an underlying health condition like:

Just because you have low hematocrit levels, doesn’t necessarily mean that you have any of the above conditions. Your doctor will likely run other medical tests and ask you about your medical history to help determine what’s actually going on.

What does it mean if your hematocrit is high?

Experiencing certain symptoms may indicate that you need a hematocrit test and that your hematocrit is high. If you’re having any of the following symptoms, you should talk with your doctor about whether or not a hematocrit test is right for you:

  • Tiredness
  • Shortness of breath
  • Flushed skin
  • Sweating
  • Dizziness
  • Joint pain
  • Itching
  • Headaches

If you’ve taken a hematocrit test and hematocrit is high, this means that you have more red blood cells than what’s considered to be healthy. High hematocrit levels could indicate underlying medical conditions like:

  • Dehydration
  • Carbon monoxide poisoning
  • Congenital heart disease
  • Bone marrow disease (polycythemia vera)
  • Scarring of the lungs
  • Not enough oxygen in the blood (often from lung conditions)
  • Erythrocytosis

Having abnormally high levels of red blood cells doesn’t necessarily mean that you have one of the conditions listed above. High hematocrit levels can mean that you might have a serious health condition like heart disease, but your doctor will run other tests to make sure you’re properly diagnosed.

How do you treat abnormal hematocrit levels?

Once you’ve taken a hematocrit test and know whether or not you have high or low hematocrit levels, the next step is figuring out the cause. Treatment will be based on how abnormal the hematocrit is and its underlying cause.

What to do for abnormally high hematocrit levels

Certain lifestyle changes, like quitting smoking and staying hydrated, can help lower high red blood cell counts. Staying hydrated is especially important because fluids help keep the blood from getting too concentrated.

Other than lifestyle changes, your doctor may prescribe a medication to help with high hematocrit levels. Blood clot medications are commonly prescribed because people with too many red blood cells have a higher risk of getting a blood clot. Aspirin is sometimes recommended by doctors because of its ability to help with blood clots.

Other medications that doctors prescribe for high hematocrit levels are likely to focus on treating the condition that’s causing the body to produce too many red blood cells, like bone marrow or heart disease. Phlebotomy (bloodletting) is a popular way to control high red blood cell counts. In phlebotomy, blood is taken from the veins to make it thinner.

What to do for abnormally low hematocrit levels

People with extremely low red blood cell counts may need to go to the doctor to get intravenous iron or blood transfusions. If there’s an underlying health condition that’s causing the body to produce less red blood cells, then medication might be needed to help stimulate the production of new red blood cells.

Some lifestyle changes can help increase red blood cell counts. Eating a variety of fresh, healthy foods that contain iron, vitamin B-12, and folic acid can prevent anemia. Taking these nutrients in supplement form can also be beneficial.

The best way to learn more about how to treat low or high hematocrit levels is to talk with your doctor or healthcare provider.